KR20180044374A - Battery Sensor - Google Patents

Abstract

There is provided a battery comprising an electrochemical unit including at least one electrochemical cell. The at least one electrochemical cell includes a cell anode, a cell cathode, and an electrolyte in contact with the cell anode and the cell cathode. The electrochemical unit further comprises a first contact electrode mounted on one surface of the electrochemical unit. Wherein the battery further comprises a second contact electrode disposed adjacent to the electrochemical unit such that the first contact electrode and the second contact electrode are positioned facing each other such that the first contact electrode and the second contact Allowing the contact resistance between the electrodes to be measured.

Description

Battery Sensor

The present invention relates to a method and apparatus for determining a state of charge (SOC) and / or a state of health (SOH) of a battery, particularly a lithium-sulfur (Li-S) .

State of Charge (SOC) / State of Health (SOH) estimation is a fundamental parameter for ensuring accurate battery usage and safe use of the battery for battery life. There are a number of techniques for monitoring these parameters, including battery voltage measurement and impedance spectroscopy, Coulomb counting methods, and the introduction or combination of various adaptive systems of such methods.

US5567541A relates to a method and apparatus for measuring the state of charge of a battery based on the volume of a battery component. In particular, US5567541A discloses the use of strain-gauges to determine the change in length of the outside circumference of a battery.

According to an embodiment of an embodiment of the present invention, there is provided a battery comprising an electrochemical unit including at least one electrochemical cell. The at least one electrochemical cell includes a cell anode, a cell cathode, and an electrolyte for establishing contact between the cell anode and the cell cathode. The electrochemical unit further comprises a first contact electrode mounted on one surface of the electrochemical unit. Wherein the battery further comprises a second contact electrode disposed adjacent to the electrochemical unit such that the first contact electrode and the second contact electrode are positioned facing each other such that the first contact electrode and the second contact The contact resistance between the electrodes is allowed to be measured.

Therefore, a contact resistance between the first contact electrode and the second contact electrode, which indicates shrinkage or expansion of the electrochemical cell during charging or discharging of the battery, can be measured. In this way, the state of charge and / or health of the battery can be determined.

The first and second contact electrodes and the second contact electrode may be electrically insulated from the electrolyte. The second contact electrode may be disposed adjacent to the first contact electrode. The second contact electrode may be in contact with the first contact electrode.

The first contact electrode may be provided on an outer surface of the electrochemical unit. The first contact electrode and the second contact electrode may not be in contact with the electrolyte.

As will be appreciated by one of ordinary skill in the art, the term "contact resistance " refers to the resistance between two electrodes due to the physical contact of the two electrodes. The contact resistance is a resistance between the first contact electrode and the second contact electrode when the first contact electrode and the second contact electrode are in contact with each other.

In one example, the first contact electrode and the second contact electrode may have surface roughness. As the contact pressure between the first contact electrode and the second contact electrode increases, the first contact electrode and the second contact electrode are more strongly pressed together, thereby increasing the surface area of the contact surface. As the surface area of the contact surface increases, the resistance of the first contact electrode and the second contact electrode as combined electrical components decreases in proportion to the applied pressure. This is because the distance between the conductive portions of the first contact electrode and the second contact electrode is reduced. In addition, the electrical surface area between the electrodes is larger because the plurality of conductive particles are packed (or contacted) with each other. This contributes to a better electrical path between the contact electrodes to lower the sensor resistance.

The electrochemical unit may be provided in a pouch. The pouch may comprise at least one electrochemical cell. Thus, the cell anode, the cell cathode, and the electrolyte are in the pouch. The first contact electrode may be provided on one surface of the pouch. The first contact electrode may be provided on an outer surface of the pouch. In one embodiment, the second contact electrode may be mounted on one surface of a battery case configured to house one or more electrochemical units.

Optionally or additionally, the battery further comprises a second electrochemical unit comprising at least one electrochemical cell comprising a cell anode, a cell cathode and an electrolyte for establishing contact between the cell anode and the cell cathode . The second contact electrode may be mounted on one surface of the second electrochemical unit. The first electrochemical unit and the second electrochemical unit may be disposed adjacent to each other.

The second electrochemical unit may be provided in the second pouch. Therefore, the cell anode, the cell cathode, and the electrolyte are in the second pouch. The second contact electrode may be provided on one surface of the second pouch. The second contact electrode may be provided on the outer surface of the second pouch. Wherein the first pouch and the second pouch are disposed adjacent to each other so that the first contact electrode and the second contact electrode are positioned facing each other such that a contact resistance between the first contact electrode and the second contact electrode It is allowed to be measured.

The battery may be a lithium-sulfur battery, and in a lithium-sulfur battery, the cell anode comprises a lithium anode, and the cell cathode comprises a mixture of an electroactive sulfur material and a conductive material. Examples of lithium-sulfur batteries are described, for example, in WO 2014/155070 and WO 2015/092384.

The lithium-sulfur cell includes, for example, a lithium anode formed from lithium metal or a lithium metal alloy, and a cathode formed from elemental sulfur or other conductive sulfur material. Such sulfur or other electroactive sulfur material is mixed with a conductive material such as carbon to improve the conductivity of the sulfur or other electroactive sulfur material. The electroactive sulfur material and the conductive material may be ground and then mixed with a solvent and a binder to form a slurry. The slurry may be applied to a current collector, such as a metal foil sheet (e.g., copper or aluminum), followed by drying to remove the solvent. The resulting structure may be calendared to form a composite structure that has been cut into the desired shape to form the cathode. A separator may be disposed on the cathode and the lithium anode may be disposed on the separator. An electrolyte is introduced into the cell to wet the cathode and the separator.

The electroactive sulfur material may include elemental sulfur, sulfur-based organic compounds, sulfur-based inorganic compounds, and sulfur-containing polymers. Preferably, elemental sulfur is used.

The solid conductive material may be any suitable conductive material. Preferably, such a solid conductive material may be formed of carbon. Examples include carbon black, carbon fiber, graphene and carbon nanotubes. Other suitable materials include metals (e.g., flakes, filings and powders) and conductive polymers. Preferably, carbon black is employed.

The lithium-sulfur cell may include an electrolyte including a lithium salt and an organic solvent. The electrolyte is present or disposed between the electrodes, allowing charge transfer between the anode and the cathode. Suitable organic solvents for use in the electrolyte include, but are not limited to, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl propyl propionate, ethyl propyl propionate, , Dimethoxyethane, 1,3-dioxolane, diglyme (2-methoxyethyl ether), tetraglyme, ethylene carbonate, propylene carbonate, butyrolactone, dioxolane, hexamethylphosphoramide, pyridine, dimethyl sulfoxide , Tributyl phosphate, trimethyl phosphate, N, N, N, N-tetraethylsulfamide, and sulfone and mixtures thereof. Sulfone, for example sulfolane, is preferred. Suitable lithium salts include lithium hexafluorophosphate (LiPF ₆ ), lithium hexafluoroacetate (LiAsF ₆ ), lithium perchlorate (LiClO ₄ ), lithium trifluoromethanesulfonimide (LiN (CF ₃ SO ₂ ) ₂ ) And lithium trifluoromethane sulfonate (CF ₃ SO ₃ Li). This lithium salt provides a charge carrying species to the electrolyte to allow the redox reaction at the electrode to take place.

When the lithium-sulfur cell is discharged, the sulfur or other electroactive sulfur material is reduced to form polysulfide species that are soluble in the electrolyte. The polysulfide species may be further reduced to form insoluble lithium sulfide. Thus, upon discharge, the composition of the cathode is changed, so that at least a portion of the cathode is dissolved in the electrolyte when the cell is discharged. This typically results in a change in the volume of the entire cell that can be measured in accordance with the embodiments described herein to provide an indication of the state of charge and / or health of the entire cell. When charged, the reaction is reversed as lithium sulphide is re-oxidized to form sulfur.

Each electrochemical unit can be separated from the adjacent unit by a separating member equipped with the contact electrode. The separating member may be provided by a wall of the pouch. The pouch may be a sealed case. The separating member may be a flexible material, for example a flexible polymeric material. In some embodiments, the separating member may be a polymer coated aluminum foil.

The separating member may include a metal foil sheet. The separating member may further include an insulating layer which insulates one side of the separating member from the other side.

The separating member may include an insulating material sheet.

Each contact electrode may be formed of an electrical conductor that is deposited on one surface of the separating member.

The conductor may comprise a conductive material. The conductive material may have a resistance value greater than 0.5 kOhm. In some embodiments, the conductive material may be a conductive pattern. When a conductive pattern is employed, the contact resistance between two contacting conductive patterns is measured and is not a resistance across the plane of each pattern or a resistance in the plane of each pattern. The conductive pattern may include a metal. In one particular embodiment, the conductive pattern may comprise a metal flake and a polymer. In another embodiment, the conductive pattern may be formed of carbon or a carbon containing material.

The conductor may include carbon. Suitable examples include carbon black, carbon fiber, graphene and / or carbon nanotubes. Preferably, carbon black is employed.

The contact electrode may be applied with a paste or slurry comprising a conductor, a binder and a solvent, and optionally a resistive material (e.g., a plastic material, a ceramic / metal mixture). By adding ceramic to the metal in the resistive material, the resistance of the resistive material can be increased. Suitable binders include PEO, PVDF, and conductive polymers. Suitable solvents include polar or nonpolar solvents (e. G., Water).

In one embodiment, the contact electrode is applied with a paste or slurry comprising carbon. Such carbon based, paste or slurry coatings may contain from 1 to 70% by weight of carbon. In one example, the paste or slurry coating contains 5 to 50 wt% carbon, preferably 10 to 40 wt% carbon. Once applied, the solvent may be substantially evaporated leaving a coating that may contain up to 100% by weight of carbon and binder.

The ratio of binder to carbon may be up to 70:30. In some embodiments, the carbon to binder ratio may be up to 50:50. In a preferred embodiment, the carbon to binder ratio is up to 40:60. Thus, once the solvent has evaporated from the slurry, the contact electrode may contain 40-70 wt% carbon, e.g., 40-50 wt% carbon.

The contact electrode may be applied to the surface of the cell, e.g., to a separating member (e.g., with a paste). The contact electrode may be applied such that the contact electrode covers a substantial portion of the surface of the cell. Thus, the contact resistance can be measured over a significant area. In one example, the separating member may take the form of a pouch, whereby each electrochemical unit is encapsulated in an insulating pouch or housing. The contact electrode may be applied to the outer surface of the pouch or housing. Each pouch or housing may be disposed adjacent to each other such that the corresponding contact electrode of each pouch or housing is positioned opposite each other. The pouches or housings may be included in the outer case. A contact electrode may be provided on the inner surface of the outer case. The pouch or housing is arranged such that the contact electrode of the pouch or housing is positioned to face the contact electrode of the outer case so that the contact resistance between the contact electrode on the pouch and the contact electrode on the outer case can be determined.

The contact electrode may be provided with contact tabs configured to contact an apparatus for measuring the contact resistance between the contact electrodes positioned facing each other. Such a battery may further include such a device.

The battery may include three or more electrochemical units.

Each electrochemical unit may include a plurality of electrochemical cells.

According to another embodiment of the present invention, there is provided a method for estimating the state of charge of the battery. The method includes receiving a current contact resistance value; Comparing the current contact resistance value with at least one previous contact resistance value corresponding to a known state of charge of the battery; And estimating a state of charge of the battery based at least in part upon comparing the current contact resistance value to the at least one previous contact resistance value.

Therefore, the state of charge of the battery is estimated using the contact resistance value. The contact resistance value may indicate the pressure on the surface of the cell.

The method may further include estimating a health state of the battery based at least in part on the estimated state of charge of the battery and the current contact resistance value.

Therefore, the health state of the battery is estimated based on the contact resistance value. The health state of the battery may be estimated based on a plurality of previous contact resistance values received in a known state of charge of each previous contact resistance value. The previous contact resistance value can be obtained from the additional battery. The additional battery may be a prototype battery.

According to one embodiment of the present invention, a method of estimating the health state of the battery is provided. The method includes receiving a current contact resistance value in a known charge state; Comparing the current contact resistance value with a plurality of previous contact resistance values each corresponding to a known charging state of the battery; And estimating the health state of the battery based at least in part upon comparing the current contact resistance value to the plurality of previous contact resistance values.

Therefore, the health state of the battery can be determined using a plurality of previous contact resistance values and a current contact resistance value when a state of charge corresponding to each contact resistance value is known.

The method may further comprise comparing the health condition of the battery to an acceptable range and determining that the battery is potentially unsafe when the health condition is out of the acceptable range.

Therefore, the safety of the battery can be determined using the health state estimation method.

According to another embodiment of the present invention, a battery management system for the battery is provided. The battery management system comprising: a controller configured to receive a current contact resistance value; At least one processor; And when executed, cause the at least one processor to compare the current contact resistance value with at least one previous contact resistance value corresponding to a known state of charge of the battery and to compare the current contact resistance value with the at least one And a memory that includes instructions for estimating a state of charge of the battery based at least in part upon comparing with a previous contact resistance value.

The memory may further include instructions that, when executed, cause the at least one processor to estimate a health state of the battery based at least in part on the estimated state of charge of the battery and the current contact resistance value.

According to another embodiment of the present invention, a method of estimating the state of charge of a cell in a lithium-sulfur battery is provided. The method comprising: receiving a current state of charge value indicating a state of charge of the cell; Comparing a first derivative of the charge state value with a first derivative of at least one previous charge state value indicative of a known charge state of the battery; And estimating a state of charge of the battery based at least in part upon comparing the first derivative of the current state of charge with the first derivative of the at least one previous state of charge.

The charge state value may indicate the degree of expansion or contraction of the cell.

The charge state value may be a pressure sensor value. The pressure sensor value may be a resistance value. The resistance value may be a contact resistance value.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 is a graph illustrating a cell thickness and voltage of a cell during the cycle life of a lithium-sulfur battery.
2 is a graph illustrating a graph showing the cell thickness and voltage of a cell during individual cycles of the cycles shown in FIG.
3 is a view illustrating a contact resistance sensor used for measuring shrinkage or expansion of an electrochemical cell.
4 is a graph illustrating a graph showing a change in the contact resistance value for a single cell during discharge for two different cycles.
Figure 5 (including Figures 5A-5B) illustrates six graphs illustrating a plurality of power factors that may be applied to the first derivative of the resistance.
6 is a diagram illustrating an assembly of a plurality of cells according to an embodiment of the present invention.

While the present invention will be described with reference to lithium-sulfur batteries, it will be understood that such lithium-sulfur batteries are equally applicable to all electrochemical batteries that expand or contract during charging or discharging.

1 is a graph illustrating a cell thickness and voltage of a cell during the cycle life of a lithium-sulfur battery. The graph shows both a change in cell voltage and a change in displacement of the cell during a subsequent discharge of the cell after about 120 cycles of charging. In lithium-sulfur batteries, it can be seen that the peak cell voltage for each cycle decreases only slightly by about 0.02 volts. In practice, this is one of the advantages of lithium-sulfur batteries in which the peak cell voltage is not significantly reduced by repeated charge / discharge cycling. Likewise, the minimum cell voltage for each cycle remains substantially constant at about 1.5V. There is a voltage change of about 0.95 volts between fully charged and fully discharged cells.

Figure 1 also shows the change in cell displacement during repeated charging and discharging of the battery. It can be seen that charge and discharge causes a change in cell displacement as a result of cell expansion and contraction due to chemical processes at the anode and cathode in the electrochemical cell. The displacement of the cell is related to the state of charge and health of the cell. As the cell expands in lithium-sulfur batteries, the displacement profile upon discharge decreases. However, the displacement increases while the cell is being charged (the cell is contracted). The cycle cycle has variable displacements over the cell life cycle due to repeated cell charge and discharge resulting in non-reversible cell expansion resulting from material deterioration and cell aging.

In particular, the change in cell displacement shows a change in the amount of expansion and contraction according to the number of cycles. For example, the 57th cycle shows a cell displacement that varies between about -1.65 millimeters and a minimum of -1.67 millimeters, which is a total cell displacement variation of about 0.02 millimeters. Relatively, in the 114th cycle, the cell displacement varies from a maximum of about -1.565 millimeters to a minimum of about -1.6 millimeters, which is about 0.035 millimeters of total cell displacement variation, nearly twice the variation seen in the 57th cycle.

It will also be appreciated that, besides the variation of the displacement range for each cycle, the minimum and maximum displacement values for each cycle exhibit an independent change over the life cycle of the cell. For example, to about the 57th cycle, the minimum displacement value for each cycle decreases from about -1.575 millimeters in the first cycle to about -1.67 millimeters in the 57th cycle, depending on the number of cycles. Beyond the 57th cycle, the minimum displacement value again increases to about -1.59 millimeters. A previous measurement of the cell expansion coefficient through a similar battery, where the health condition of the battery is known to exhibit substantially the same cell expansion life cycle, when the cell expansion coefficient can be determined for the battery at the maximum or minimum cell displacement value or other known reference point As will be appreciated by those skilled in the art. In Fig. 1, the cell expansion coefficient is a cell displacement. This is useful because it allows the number of remaining charge cycles for a given battery to be calculated before a given battery has to be replaced to meet its useful life. In some batteries, this can be used even if the battery is not fully charged and discharged in previous cycles, so that the discharge history of the battery provides predicted values of the cell expansion coefficient used to estimate the health condition of the battery But does not match the discharge history of a similar battery used for the battery.

It will further be appreciated that, in some circumstances, the cell expansion coefficient measured at the battery will deviate from the range of cell expansion coefficients observed at the expected values of the cell expansion coefficient. This may indicate a defective battery that is replaceable for safety or for efficiency.

Figure 2 is a graph illustrating a cell thickness and voltage of a cell during an individual cycle for a lithium-sulfur battery. Although the graph of FIG. 1 illustrates data useful for determining the health state of the battery, the graph of FIG. 2 illustrates data useful for determining the state of charge of the battery. It should be noted that data of two different batteries are shown in Figs. 1 and 2. It can be seen that the cell voltage changes nonlinearly from a maximum initial voltage of about 2.45 volts when fully charged to a minimum voltage of about 1.50 volts when fully discharged. From about 75% charge (25% discharge) to about 25% charge (75% discharge), there is a voltage plateau, in which case the voltage is reduced to 75 % ≪ / RTI > to about 2.05 volts at about 50% charge. This nonlinear behavior is also non-deterministic. For example, a cell voltage of about 2.05 volts may be equal to a battery charge level of about 80 percent or less than 50 percent. Therefore, it is impractical and unreliable to use the cell voltage to estimate the state of charge of the lithium-sulfur battery.

The displacement also varies nonlinearly from an initial maximum of about -1.613 millimeters to a minimum of about -1.635 millimeters. However, unlike the cell voltage, the cell expansion coefficient in the form of the displacement value is substantially deterministic. In other words, there is a 1: 1 relationship between the state of charge of the battery and the cell displacement value. A polynomial function may be suitable as the data to provide a model of the state of charge of the battery as a function of the cell displacement value.

However, due to size and structure limitations, it is impractical to mount a linear variable differential transformer (LVDT) on the battery. Therefore, alternative solutions are needed. A particularly advantageous method for measuring the cell expansion coefficient is to use a thin film pressure sensor. The pressure sensor is disposed on one surface of the cell and on another defined surface. Thus, when the chemical composition of the compounds in the cell is changed by the chemical reactions occurring in the cell, the pressure change in the cell prompts the cell to expand or contract. The cell is substantially prevented from expanding by the defined surface, thereby creating a pressure change between the cell surface and the defined surface. As will be appreciated, the confined surface may be a battery casing or a cell wall of an additional electrochemical cell. Although an arbitrary contact pressure sensor can be used to measure the contact pressure on the wall of the cell, this embodiment uses a thin film pressure sensor formed of a pair of metal foil electrodes. The sensors are typically less than 1 mm in thickness and can be installed between the cells without compromising the internal structure of the battery.

3 is a diagram illustrating a contact resistance sensor used to measure shrinkage or expansion of an electrochemical cell. The pressure sensor comprising a conductor pattern, the conductor pattern being mounted in the form of a resistance pattern on a first surface to form a first sensor electrode, the conductor pattern being disposed on an additional conductor pattern and having an additional resistance And is mounted in the form of a pattern to form a second electrode. The contact resistance is a resistance between the first sensor electrode and the second sensor electrode when the first sensor electrode and the second sensor electrode come into contact with each other. The first and second sensor electrodes have a surface roughness. As the contact pressure increases, the first and second sensor electrodes are firmly pressed against each other to increase the surface area of the contact surface. As the surface area of the contact surface increases, the resistance of the sensor (electrode pair) decreases in proportion to the pressurized pressure. This is because the distance between the conductive portions of the first and second sensor electrodes is reduced. In addition, the electrical surface area between the electrodes becomes larger because the number of conductive particles to be packed (or brought into contact with each other) increases. This contributes to a better electrical path between the sensor electrodes to lower the sensor resistance. In one embodiment, the conductor pattern electrode is formed of a strain gauge. Although strain gauges are typically designed to exhibit a change in resistance due to stress applied in the direction of alignment of parallel conductor lines forming a strain gage, in the present embodiment strain gauges To form a pressure sensor that is sensitive to pressure variations between the two strain gauges. The strain gages may comprise carbon-based inks. Although strain gauges have been described as being used to form the first and second sensor electrodes, it is known that when the increase in pressure perpendicular to the surface of the sensor electrode due to surface roughness results in a decrease in the contact resistance, Any conductive film or pad may be used. It will also be appreciated that there are many techniques for measuring and amplifying changes in resistance. The present embodiment uses a Wheatstone bridge having two individual sensor electrodes forming the first and second sensor electrodes, respectively, with the first and second sensor electrodes having known resistances R1, R2, R3, R4 .

The present embodiment locates the contact resistance sensor substantially at the center of the cell surface, although a pressure sensor in the form of the contact resistance sensor may be disposed virtually anywhere on the cell surface between additional defined surfaces. Although only a single contact resistance sensor is described in this embodiment, it will be appreciated that a plurality of contact resistance sensors may be used between the plurality of electrochemical cells in the battery. In some embodiments, a plurality of contact resistance sensors may be disposed at different locations around the surface of the electrochemical cell. In one embodiment, the pressure sensor is formed of a slurry applied to the electrochemical cell. The slurry will be further described with reference to FIG.

4 is a graph illustrating a graph showing changes in the contact resistance value for a single cell equipped with a contact resistance sensor during discharging for the second and tenth cycles; The graph shows that the cell voltage relationship with the discharge did not substantially change between the cycles as expected in Fig. On the other hand, the resistance value measured during discharging differs depending on the number of cycles. Indeed, the resistance measurement for the tenth cycle appears to exhibit a higher resistance than the resistance measurement for the first cycle when the battery is fully charged and appears to exhibit a lower resistance as compared to the first cycle when the battery is fully discharged . This indicates that the cell pressure change is greater in the first cycle than in the tenth cycle. As discussed previously, this is due to an increase in the irreversibility in chemical reactions within the cell leading to cell expansion.

The graph further includes a polynomial resistance trend line suitable for resistance measurement for each cycle. The resistance trend line may be expressed as a fifth order polynomial. This represents four plateau (more is possible) and four knee changes. These correspond to the Charge State (SOC) characteristics, where the knees (first priority marks) are at the beginning of the first voltage plate at about 2.4 V, at the end of the first voltage plate at about 2 V, It appears at approximately 2.05V at the highest voltage point of the second plateau and before the high resistance discharge plateau at approximately 2V. It is important that all such readings for resistance characteristics are not linear and the values of the same voltage output (excluding the first knee) are about 200 Ohm to 600 Ohm difference. The sensitivity of the resistance characteristic can be improved by a high sampling rate, which in the present case the sample interval is 5 minutes.

To determine the change in slope for the resistance characteristic, the battery management system (BMS) can calculate the first derivative of the resistance dR / dt. The quality of the derivatives As a result, the perception of changes is determined by the resistance sampling rate.

5 is a diagram illustrating six graphs illustrating a plurality of power factors that may be applied to a first order derivative of a resistor. The multiplication process can be performed by the BMS. By increasing the dR / dt samples to a power factor, the change in resistance characteristics can be "magnified" to provide the local maximum value with discernible values. These values can be used by the BMS to predict changes in resistance characteristics (knee and plateau) and consequently changes in the SOC of the battery.

Small power factor (n = 0.5, 1, 2) are good for cell discharge initiation and higher power factors are good for discharge middle and end. The BMS can perform a first order derivative manipulation by various power factors simultaneously searching for peaks of the results. The first "peak" results up to 10 ¹ Ohm ⁿ / h will present the second knee on the resistance curve, the results of about 10 ² Ohm ⁿ / h will give a third drift, and about 10 ³ Ohm The results of ⁿ / h show the fourth knee. With the discharge voltage measurement, the BMS can accurately estimate the SOC of the cell / battery during discharge. The graphs in FIG. 5 are annotated with labels that show specific portions of data representing the first, second, third, and fourth knees. As can be seen, the values of dR / dt for the first and second knees become most noticeable in the data when dR / dt rises to a power factor of 0.5. The value of dR / dt for the third knee becomes most noticeable in the data when dR / dt is increased by a power factor of 1. The value of dR / dt for the fourth knee is most pronounced in the data when dR / dt rises at a power factor of 5, but is also particularly emphasized by power factors of 2, 3 and 4.

Although FIG. 5 relates to a first derivative of the resistance measurement, it will be appreciated that a similar technique may be applied to calculate the first derivative of any other cell expansion coefficient.

Although the graphs shown in FIGS. 2 and 4 show a situation in which the battery is actively discharged using a load, when the battery is in a rest period during which the battery is self-discharged because the load is not connected, It is also important to do. In one embodiment of the lithium-sulfur battery used to generate the graphs of Figures 2 and 4, the total capacity of the battery was found to be 1.65 Ah. If the battery was in a 50-hour self-discharge dwell period before it was fully discharged, the remaining capacity was found to be 1.35 Ah. In this particular battery, it has been found that most of the self-discharge occurs within the first 10-20 hours of the stabilization of the resistance measured by the contact resistance sensor. The stabilized resistance indicates that the cell does not shrink even when it expands, suggesting that self discharge of the battery is negligible.

6 is a diagram illustrating an assembly of a plurality of cells in accordance with an embodiment of the present invention. The first cell A is provided with a first sensor electrode A on the first side and a second sensor electrode B on the second side opposite to the first side. The second cell B is substantially similar to the first cell A having the first and second sensor electrodes A, B. The second cell B is provided adjacent to the first cell A so that the second sensor electrode B of the first cell A and the second sensor electrode A of the second cell B face each other To form a pressure sensor in the form of a contact resistance sensor (C). The contact resistance sensor C indicates a reduced resistance as the pressure in the first cell A or the pressure in the second cell B increases to increase the pressure of the contact resistance sensor. Although this embodiment is characterized by two cells, more cells may be provided, each cell having a first sensor electrode A and a second sensor electrode B that form a contact resistance sensor between adjacent cells . In some embodiments, a plurality of cells may be provided in one or more electrochemical units. Each electrochemical unit is separated from adjacent electrochemical units by a separating member in the form of a pouch. In this way, the first sensor electrode (A) can be mounted on a first pouch containing a first electrochemical unit, and the second sensor electrode (B) can be mounted on a second pouch containing a second electrochemical unit And can be mounted on the pouch. The separating member is typically not in contact with the electrolyte of the electrochemical cell.

The first sensor electrode A and the second sensor electrode B may be formed by an active cell surface formed during the fabrication of the cell. It will be appreciated that the active cell surface is typically any surface of an electrochemical cell that can act as a sensor for determining the state of charge state in the form of a sensor for determining the expansion or contraction coefficient. In this way, the sensor is already built into the cell itself rather than being a separate component. In this embodiment, the active cell surface is formed by priming the cell surface area (outer surface of the pouch) with conductive carbon paint and attaching sensor contacts thereto. On the conductive carbon paint, a sensor electrode formed of a carbon-based slurry is applied. Methods of applying primers and slurries such as printing, spraying or blade spreading are currently known.

In this embodiment, a sulfur cathode slurry was used to produce active cell surfaces. Typically, the slurry blend is a conductor (high surface area carbon, such as carbon black); Insulators (e.g., elemental sulfur, polymers, etc.); A binder (e.g., PEO); And a solvent. In one embodiment, the slurry blend comprises 10% barbon black, 70% sulfur and 20% PEO (per weight). It will be appreciated that the slurry blend may have a different blend after application of the slurry blend to the cell surface area. For example, the solvent in the slurry blend may substantially evaporate during application of the slurry blend to the cell surface area.

Thus, the active cell surface should provide desirable characteristics and a high variable resistance of about 0.5 kOhm to 10 kOhm. It is advantageous for the resistance characteristic of the pressure sensor to have a nonlinear resistance change with respect to the linear pressure filling. This is because the nonlinear behavior is characterized by plateau and tilt variations that are identifiable using the derivative method described above and are related to the state of charge of the battery.

It will be appreciated that the sensor electrodes are not in contact with the electrolyte of the electrochemical cell. The sensor electrodes are typically provided outside the electrochemical cell.

Although this disclosure refers to the cell expansion coefficient, it should be understood that there are a number of variations that are indicative of a change in pressure or volume within the cell as a result of a chemical reaction at the anode and / or cathode in the electrochemical cell as a result of a charging or discharging process It will be appreciated that other cell expansion coefficients may be used. For example, the sensors may be mounted to the cell to measure the change in length of the side of the cell. Alternatively, sensors may be mounted in the cell to measure the change in pressure exerted by the cell casing on the battery casing surrounding the cell casing. In this way, the sensor value indicative of the pressure change in the electrochemical cell can still be referred to as the cell expansion coefficient even when the electrochemical cell is kept at substantially the same volume with increasing pressure in the electrochemical cell. In other words, if the pressure in the electrochemical cell is kept constant, the electrochemical cell will have to change its volume.

Throughout the description and claims of this specification, the words "include" and "accept" and their variations are intended to include "(-) but not limited to (-) Quot; and is not intended to exclude (and not exclude) other parts, additives, components, integers, or steps. Throughout the description and claims of this specification, the singular forms include the plural unless the context otherwise requires. In particular, where infinitive is used, it should be understood that the present specification contemplates the plural and singular, unless the context requires otherwise.

Any feature, integer, feature, compound, chemical moiety, or group described in connection with a particular embodiment, example, or example of the invention may be combined with any other embodiment, example, or example described herein It should be understood that it is applicable. All of the features disclosed in the specification (including any accompanying claims, abstract, and drawings) and / or any of the methods or process steps disclosed thereby may be combined in any combination, And / or combinations where at least some of the steps are mutually exclusive. The present invention is not limited to the details of any of the above-described embodiments. The present invention is not intended to be limited to any novel features, or any novel combination, of the features disclosed herein (including any accompanying claims, abstract, and drawings), or any method Or any of the steps of the process, or any novel combination thereof.

The reader's attention is directed to all papers and documents presented at the same time as the present specification with respect to the present application or disclosed prior to the present specification and disclosed in the disclosure check of the present specification and the contents of all such articles and documents are hereby incorporated by reference Is supplemented.

Claims (25)

As a battery,
a) at least one electrochemical cell comprising i) a cell anode, a cell cathode and an electrolyte in contact with the cell anode and the cell cathode, and ii) a first contact electrode mounted on the surface of the electrochemical unit An electrochemical unit; And
b) a second contact electrode disposed adjacent to the electrochemical unit;
Wherein the first and second contact electrodes are positioned opposite each other to allow the contact resistance between the first contact electrode and the second contact electrode to be measured. The method according to claim 1,
And the second contact electrode is mounted on a surface of a battery case configured to store the electrochemical unit. The method according to claim 1,
The battery includes:
A second electrochemical unit comprising a cell anode, a cell cathode, and at least one electrochemical cell comprising an electrolyte in contact with said cell anode and said cell cathode;
Further comprising:
And the second contact electrode is mounted on a surface of the second electrochemical unit. 4. The method according to any one of claims 1 to 3,
The battery is a lithium-sulfur battery,
Wherein the cell anode comprises a lithium anode,
Wherein the cell cathode comprises a mixture of an electroactive sulfur material and a conductive material. The method according to claim 3 or 4,
Wherein each electrochemical unit is separated from an adjacent electrochemical unit by a separating member equipped with a contact electrode. 6. The method of claim 5,
Wherein the separating member comprises a sheet of metal foil. The battery according to claim 5 or 6, wherein the separating member comprises an insulating sheet material. 8. The method according to any one of claims 5 to 7,
Wherein the contact electrode is formed of a conductor that is deposited on a surface of the separating member. 9. The method of claim 8,
Wherein the conductor comprises a conductor pattern. 9. The method of claim 8,
Wherein the conductor comprises carbon black. 11. The method according to claim 8 or 10,
Wherein the contact electrode is applied as a paste comprising a conductor and a binder. 12. The method according to any one of claims 1 to 11,
Wherein the contact electrodes are provided with contact tabs configured to contact an apparatus for measuring contact resistance between opposing contact electrodes. 13. The method of claim 12,
Wherein the battery further comprises the device. 14. The method according to any one of claims 1 to 13,
A battery comprising more than two electrochemical units. 15. The method of claim 14,
Each unit comprising a plurality of electrochemical cells. 16. A method for estimating a state of charge of a battery according to any one of claims 1 to 15,
Receiving a current contact resistance value;
Comparing the current contact resistance value with at least one previous contact resistance value corresponding to a known state of charge of the battery; And
Estimating a state of charge of the battery based at least in part on comparing the current contact resistance value to the at least one previous contact resistance value;
And estimating a state of charge of the battery. 17. The method of claim 16,
The method comprises:
Estimating a health state of the battery based at least in part on the current contact resistance value and the estimated state of charge of the battery;
Further comprising the steps of: estimating a state of charge of the battery. A method for estimating a health condition of a battery,
The method comprises:
Receiving a current contact resistance value in a known charge state;
Comparing the current contact resistance value with a plurality of previous contact resistance values each corresponding to a known charging state of the battery; And
Estimating a health condition of the battery based at least in part on comparing the current contact resistance value to the plurality of previous contact resistance values;
And estimating a health condition of the battery. 19. The method of claim 18,
The method comprises:
Comparing the health condition of the battery to an acceptable range; And
Determining that the battery is potentially unsafe if the health condition is out of the acceptable range;
Further comprising: determining a health condition of the battery. 16. A battery management system for a battery according to any one of claims 1 to 15,
The battery management system includes:
A controller configured to receive a current contact resistance value;
At least one processor;
Wherein the at least one processor, when executed,
Comparing the current contact resistance value with at least one previous contact resistance value corresponding to a known state of charge of the battery; And
Performing a step of estimating a state of charge of the battery based at least in part on comparing the current contact resistance value to the at least one previous contact resistance value;
And a battery charging system. 21. The method of claim 20,
The memory further comprises instructions to cause the at least one processor to perform a step of estimating a health condition of the battery based at least in part on the current contact resistance value and an estimated state of charge of the battery when executed, , Battery charging system. A method for estimating a state of charge of a cell in a lithium-sulfur battery,
The method comprises:
Receiving a current state of charge value indicating a state of charge of the cell;
Comparing a first derivative of the charge state value with a first derivative of at least one previous charge state value indicative of a known charge state of the battery; And
Estimating a state of charge of the battery based at least in part on comparing a first derivative of the current state of charge to a first derivative of the at least one previous state of charge;
/ RTI >
Wherein the state of charge values are pressure sensor values. 23. The method of claim 22,
Wherein the charge state value indicates the degree of expansion or contraction of the cell. 24. The method according to claim 22 or 23,
Wherein the pressure sensor values are resistance values. 25. The method of claim 24,
Wherein the resistance values are contact resistance values.

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